Tide & Current

Discussion about the files. How to improve Tides and their use.

The harmonics data (value and angle) must be listed in the same orderly way as Number of constituents in the header of the harmonic file, that is:-

92
#
# Constituent speeds
# Format: identifier [whitespace] speed [CR]
# Speed is in degrees per solar hour.
# Identifier is just a name for the constituent. They are for
# readability only; XTide assumes that the constituents will be listed
# in the same order throughout this file.
J1 15.5854433
K1 15.0410686
K2 30.0821373
L2 29.5284789
M2 28.9841042
etc...

The Harmonic.idx file relies upon the Harmonic (no extension) file….but yes, indeed it contains a changelog at the beginning.

The harmonic.idx

# TROIS-RIVIERES_03360, Quebec, CANADA 46d20.1'N 72d32.6'W
# METERS
# CANADIAN DATA, TZ+5.0
# Data 20.8years(1995-2015)
# !units: meters
# !longitude: -72.5392
# !latitude: 46.3435
TROIS-RIVIERES, Quebec
-05:00 :America/Montreal
1.1580 meters
J1 0.0008 020.50
K1 0.0130 011.55
K2 0.0004 229.69
L2 0.0035 071.00
M2 0.1439 002.19
etc...

the header of each part must be included prior to listing the data.
It is a bit complicated for a non intiated, but easy to manage once you have learn.
Further more the Arguments and node factors in the harmonic file must be listed in the same order. In the xtide file it start in 1700 but it is not necessary to do so. I have cut it to 1970, Unix platform require 1970.

For the rest it require the Analysis program for the hourly or 15 min or else program. Also one can add data in the harmonic.idx using offset, but one must know which station the offset is using. Sometimes there are lot of differences with the actual recording as evething depend on the lenht of the observation period.

So, in order word, one must know how to use his jugement.

Best Regards. P_Dub

Ideas

An idea, Opencpn is nowadays able to browse to and select from various tidal data files, so instead of using one file to cover the world, perhaps someday, it'd be best to cut these up into localities? and load them as required from folders.. They load faster and are easier to “play with” too. HappySeagull